Clean up polynomial constructor

[jdemeyer]

This ticket cleans up the PolynomialRing() function in many ways. Mainly:

1. Use normalize_names() as much as possible to deal with variable names.

2. Fix indentation in docstring.

3. Pass arguments like sparse and implementation as **kwds to the single-variate or multi-variate polynomial constructor.

4. Make the code easier to understand.

5. Allow PolynomialRing(..., implementation="singular") which forces Singular. This allows simplifying some code in src/sage/algebras/free_algebra.py which currently needs to jump through hoops to get a MPolynomialRing_libsingular.

6. Check more error conditions, for example currently we have

sage: PolynomialRing(QQ, name="x", names="y")
Univariate Polynomial Ring in y over Rational Field

7. Change some arguments of PolynomialRing() to keyword-only arguments. This does break some existing uses of PolynomialRing(), although much more likely in library code and not user code (some code in Sage gets this even wrong and was passing sparse="lex" instead of order="lex")

Apart from items 6 and 7, no existing functionality is changed.

CC: @tscrim

Component: algebra

Author: Jeroen Demeyer

Branch/Commit: fc75734

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/23338

[tscrim]

comment:1

+1

[jdemeyer]

Branch: u/jdemeyer/clean_up_polynomial_constructor

[jdemeyer]

Commit: 883d507

[jdemeyer]

comment:3

First version, not finished or tested yet. But feel free to comment...

---

New commits:

883d507

Clean up PolynomialRing() constructor

[jdemeyer]

Description changed:

--- 
+++ 
@@ -1 +1,11 @@
+This ticket cleans up the `PolynomialRing()` function in many ways. Mainly:
 
+1. Use `normalize_names()` as much as possible to deal with variable names.
+
+2. Fix indentation in docstring.
+
+3. Pass arguments like `sparse` and `implementation` as `**kwds` to the single-variate or multi-variate polynomial constructor.
+
+4. Make the code easier to understand.
+
+No existing functionality is changed, this is just a clean-up.

[jdemeyer]

Description changed:

--- 
+++ 
@@ -8,4 +8,11 @@
 
 4. Make the code easier to understand.
 
+5. Check more error conditions, for example currently we have
+
+```
+sage: PolynomialRing(QQ, name="x", names="y")
+Univariate Polynomial Ring in y over Rational Field
+```
+
 No existing functionality is changed, this is just a clean-up.

[jdemeyer]

Description changed:

--- 
+++ 
@@ -15,4 +15,4 @@
 Univariate Polynomial Ring in y over Rational Field
 ```
 
-No existing functionality is changed, this is just a clean-up.
+No existing functionality is changed (except for 5.): this is just a clean-up.

[jdemeyer]

Description changed:

--- 
+++ 
@@ -15,4 +15,6 @@
 Univariate Polynomial Ring in y over Rational Field
 ```
 
-No existing functionality is changed (except for 5.): this is just a clean-up.
+6. Change some arguments of `PolynomialRing()` to keyword-only arguments. This does break some existing uses of `PolynomialRing()` (some even wrong: some Singular code was passing `sparse="lex"` instead or `order="lex"`)
+
+Apart from items 5 and 6, no existing functionality is changed: this is just a clean-up.

[jdemeyer]

Description changed:

--- 
+++ 
@@ -8,13 +8,15 @@
 
 4. Make the code easier to understand.
 
-5. Check more error conditions, for example currently we have
+5. Add a new keyword argument `multivariate` to force a multivariate polynomial ring, even if there is only 1 variable.
+
+6. Check more error conditions, for example currently we have
 
 ```
 sage: PolynomialRing(QQ, name="x", names="y")
 Univariate Polynomial Ring in y over Rational Field
 ```
 
-6. Change some arguments of `PolynomialRing()` to keyword-only arguments. This does break some existing uses of `PolynomialRing()` (some even wrong: some Singular code was passing `sparse="lex"` instead or `order="lex"`)
+7. Change some arguments of `PolynomialRing()` to keyword-only arguments. This does break some existing uses of `PolynomialRing()` (some even wrong: some Singular code was passing `sparse="lex"` instead or `order="lex"`)
 
-Apart from items 5 and 6, no existing functionality is changed: this is just a clean-up.
+Apart from items 6 and 7, no existing functionality is changed.

[jdemeyer]

Description changed:

--- 
+++ 
@@ -8,7 +8,7 @@
 
 4. Make the code easier to understand.
 
-5. Add a new keyword argument `multivariate` to force a multivariate polynomial ring, even if there is only 1 variable.
+5. Allow `PolynomialRing(..., implementation="singular")` which forces Singular. This allows simplifying some code in `src/sage/algebras/free_algebra.py` which currently needs to jump through hoops to get a `MPolynomialRing_libsingular`.
 
 6. Check more error conditions, for example currently we have
 

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

2f8a591

Clean up PolynomialRing() constructor